Interpreter.h pending when using Qt Global Object in QML

I run next QML with QmlViewer (C++):

Rectangle {
    border.color: Qt.darker("Red")
}

When application close, debugger shows "Interpreter.h" at string #80:

77        Opcode getOpcode(OpcodeID id)
78        {
79            #if HAVE(COMPUTED_GOTO)
80                return m_opcodeTable[id];
81            #else
82                return id;
83            #endif
84        }

It happens always when Qt global object methods using in QML (Qt.darker(), Qt.lighter() etc).
I don't know, is this a bug or no, but there are no visible exceptions when I run my application .exe file